In recent years, in a random access memory (RAM) circuit, redundancy processing used for relief of a defective bit or an electrical fuse element used for an identification number for identifying each chip increases.
The electrical fuse element is a storage element (hereinafter, referred to as one time programming (OTP) element) in which only single writing is electrically performed. The electrical fuse element is connected to a terminal to which a predetermined write voltage is applied and a write transistor. When the predetermined write voltage is applied and the write transistor is kept in an on state by a signal for controlling writing as in a write enable (WE) signal, a current flows through the electrical fuse element. This current permits the electrical fuse element to be broken and placed in a write state.
Conventionally, there is used a technology in which in order that a voltage in a write line may be prevented from rising up upon a fuse as a write object being broken, the other fuses also may be prevented from being broken, and false writing may be prevented from occurring, a voltage in a write line is clamped so as not to be equal to or more than a fixed voltage.
Also, there is known a technology in which in order that false break of an electrical fuse element may be prevented during occurrence of electrostatic discharge (ESD), a diode for flowing a surge current of ESD is provided to prevent an inflow of a surge current to the electrical fuse element.    Japanese Laid-open Patent publication No. 53-007142    Japanese Laid-open Patent publication No. 2009-177044    Japanese Laid-open Patent publication No. 2009-157981    Japanese Laid-open Patent publication No. 08-321197
When some unintentional current flows through the above-described OTP element, false writing may occur.
For example, when abnormality occurs in a write voltage and it becomes an overvoltage, an influence may be exerted also on a signal for controlling a write transistor. In this case, even when a writing operation is not performed, the write transistor cannot be kept in an off state by a false operation of a circuit for controlling itself. As a result, an unintentional current may flow through the above-described OTP element.